Low voltage gas discharge lamps using a thermal type of hot cathode, and requiring a ballast, are known to the art. Such lamps rely upon an elevated temperature of the cathode for electron emission and normally require relatively high starting voltages. Such lamps have life expectancies at best of about 2000 hours.
Improvement in life expectancy can be anticipated using cool, or cold, cathodes wherein electron emission is a chemical at moderately low temperatures.
A very recently proposed low voltage, cold cathode fluorescent lamp using externally applied alternating current and having internal electrode structures using alternating current is described in my copending U.S. patent Application, Ser. No. 871,605, filed Jan. 23, 1978, now U.S. Pat. No. 4,158,153. Such lamps must normally be operated using a 220 volt, 60 cycle A-C input voltage and cannot be readily manufactured for use with standard 110 volt, 60 cycle A-C input voltage as found in operating incandescent lamps in the home. Moreover, the efficiency of such operation, as in the multi-column structures described in my above-mentioned application, is less than desired since each column only operates during one-half of each A.C. voltage cycle and the light output as a function of input power is not as high as could be desired, even though life expectancy is improved over previously suggested lamps of that type.
It is desirable to design a fluorescent lamp which can operate at A.C. input voltages of 110 volts, 60 cycles, for example, using cold cathodes, and which can achieve high efficiency (lumen output per watt input) and long life (e.g. well over 10,000 hours of effective operation).